Johnson Controls F261KFH-V02C Penn F261 Series Low-Flow Model Flow Switch with Type 3R (NEMA) Enclosure, 3/4". x 3/4" External NPTF Inlet and Outlet: Amazon.com: Industrial & Scientific
Johnson Controls F61KB-11C Flow Switch | eBay
CNT0132E Flow Switch - GSD HVAC Chiller Spare Parts